Process for chemically graining lithographic plates



United States l atent' C 3,220,899 PROCESS FOR CHEMICALLY GRG LITHOGRAPHHC PLATES Robert F. Leonard, East Rockaway, N.Y., assignor to Litho Chemical & Supply Co., Inc., Lynbrook, N.Y., a corporation of New York No Drawing. Filed Dec. 20, 1962, Ser. No. 245,981

13 Claims. (Cl. 15623) The present invention relates to the graining of lithographic plates and more particularly to a process for chemically graining aluminum lithographic plates on both sides simultaneously to produce a superior grain structure on such plates.

This application is a continuation-in-part of my copending application Serial No. 218,865, filed August 23, 1962, now abandoned.

Successful planographic printing from metal plates depends upon the immiscibility of oil and water and especially upon the preferential retention of a greasy imageforming substance by the image areas and a similar retention of an aqueous dampening fluid by the non-image areas. For lithographic purposes, metal plates such as those of aluminum are usually roughened or grained to minimize the attritional effect of the ink rollers on the image and to prevent the rollers from causing too great a reduction in the film of moisture which must be retained to prevent ink contamination of the non-printing portions of the plates.

In accordance with existing practices, metal lithographic plates are subjected either to marble graining or to brush graining in order to obtain a surface which will retain the image and which will hold a thin film of moisture on the non-image areas. In marble graining a plurality of marbles are agitated in contact with the plate surface in the presence of moisture and a powdered abrasive. This is a rather expensive process which requires considerable skill and experience on the part of the operator in order to obtain satisfactory graining. More recently, the brush graining technique has been adopted as an improved approach to mechanical graining and in this procedure the metal sheet is acted upon by rotating or revolving bristle brushes ordinarily in the presence of moisture and powdered abrasive. While brush graining is in some respects preferable to marble graining, it re quires costly brush graining equipment and still necessitates the use of skilled labor.

It is also known to grain metal lithographic plates chemically, but the grain produced in this way is far inferior to that produced by mechanical graining and, hence, has not proved to be satisfactory nor has it gone into extensive use. This is primarily due to the fact that chemical graining as heretofore carried out produces such a fine grain that it is of very little value and in the case of caustic etching, an unsatisfactory pebbly or nodular surface results. Alkaline etchants in general tend to produce an undesirably pitted aluminum surface with the pits in a most irregular pattern. Acid etchants are very likely to level the metal surface of the lithographic plates rather than to roughen them.

The present invention is predicated upon the discovery that by subjecting aluminum lithographic plates to a certain sequence of etchants, an idea grain is produced. Chemical graining according to the present invention is molecular in nature, by which term is meant chemical graining of various types wherein there is movement of molecules or atoms in contrast to abrasive graining which removes relatively large pieces of material from the metal surfaces.

In general, the present invention comprises a process of subjecting an aluminum lithographic plate first to an alkaline etchant, then to an acid etchant, and then again 3,220,899 Patented Nov. 30, 1965 to analkaline etchant. It has been found that this new combinationof etching treatments produces new and unobvious results whichhave not heretofore been obtained and makes possible the production of aluminum lithographic plates with a vastly superior type ofgrain structure. By combining the etchants the grain on the alu'-' minum plates is made up of tiny hills and valleys in which the valleys or depressions have U-shaped bottoms, and the hills or raised portions have straight sides and a minimum of surface area at the highest elevation. The hills and valleys are so located that there are no level areas in between. The combination of etchants has the further advantage in that it removes a minimum of metal which is economically important, but still obscures the rolling mill marks present in the original aluminum sheets. A still further advantage of importance is that the finished chemically grained plates are uniform and streak free.

According to the present invention an aluminum lithographic plate is immersed in an alkaline etching bath to produce a pitted surface, then immersed in an acid bath which deepens the pits and produces hills and valleys with sharp peaks and the thus-treated plate is then again subjected to immersion in an alkaline bath to remove the fine fragile peaks and dissolve the water-insoluble film left by the acid etching bath. After the lithographic plate has been successively immersed in the foregoing combination of etching baths, the thus molecularly or chemically grained plate is immersed in a non-etching acid bath to remove the smut produced by the final alkaline etching bath. Since the aluminum plate is fully immersed and/ or passed through these etching baths both sides of the plate are simultaneously grained in contrast to mechanical graining which acts only upon one side of the metal sheet or plate. The alkaline etching baths are based upon sodium hydroxide or potassium hydroxide and are essentially aqueous solutions of sodium hydroxide or potassium hydroxide with or without additional components as hereinafter specified and wherein the water is deionized. The two alkaline etching baths may be identical or different. The acid etching bath is essentially an aqueous solution of a mineral acid such as hydrochloric acid, nitric acid, hydrofluoric acid, phosphoric acid, fluosilic acid, hydrobromic acid, sulfuric acid, or combinations thereof.

It has further been found that the etching procedure can best be carried out within certain relatively narrow and critically significant temperature and time ranges, that the individual components in both the alkaline and acid etchants can be varied as to proportions or concentration within certain hereinafter prescribed limits and that within those ranges and limits optimum results are obtained without appreciably affecting the performance of the etchants due to the permissible variations.

The invention is illustrated by the following nonlimitative examples which represent the best mode of carrying out the invention presently known.

Example I Water (deionized) liters 66.68 Sodium hydroxide kilograrns 5.80 Glycerine liters" 33.34

Liters Water (deionized) 48.40 Phosphoric acid (85%) 48.40 Hydrofluoric acid (53%) 3.20

The sheet was then removed from the acid etchant, rinsed thoroughly with deiozined water at room temperature and then immersed in the same alkaline etchant described above under the same conditions of time, temperature and proportions. After the sheet had been removed from the last alkaline etchant it was rinsed thoroughly with deionized water at room temperature and immersed in a desrnutting bath at room temperature for thirty seconds, the desrnutting bath being composed of 50 liters of deionized water and 50 liters of 70 percent nitric acid. Upon removal of the sheet from the desrnutting bath it was thoroughly rinsed with deionized water at room temperature and dried by forced air.

Example 11 An aluminum sheet identical with that of Example I was immersed for one to three minutes, preferably two minutes, at a temperature of 50 C. to 70 C., preferably 60 C., in an alkaline etchant prepared by mixing the following components in the order listed and in the proportions stated, which proportions can be varied within a range from +20 percent to 20 percent:

Water (deionized) liters 66.68 Sodium hydroxide kilograms 5.80 Glycerine liters 33.34

After the sheet had been removed from the alkaline etchant it was rinsed thoroughly with deionized water at room temperature and immersed for ten to twenty seconds, preferably fifteen seconds, at a temperature of 55 C. to 75 C., preferably 65 C., in an acid etchant prepared by mixing the following components in the order listed and in the proportions stated wherein the 36 percent hydrochloric acid can be varied within the range from +15 percent to -15 percent:

Liters Water (deionized) 67 Hydrochloric acid (36%) 33 After removal from the acid etchant the sheet was rinsed thoroughly with deionized water at room temperature and immersed for one to three minutes, preferably two minutes, at a temperature of 67 to 87 C., preferably 77 C., in an alkaline etchant prepared by mixing the following components in the order listed and in the proportions stated, which proportions can be varied Within a range from +20 percent to 20 percent:

Water (deionized) liters 57.6 Sodium hydroxide kilograms 24.8

The same procedure was carried out as in Example I and with the same permissible variations except that the acid etchant Was prepared by mixing the following components in the order listed and in the proportions stated, which proportions can be varied within a range from +20 percent to 20 percent:

Liters Water (deionized) 48.40 Phosphoric acid (85%) 48.40 Hydrochloric acid (36%) 3.20

It is to be understood that the invention is not limited to the particular alkaline and acid etching baths set forth in the foregoing examples since it has further been found that other alkaline and acid etchants can be equally well employed.

Additional alkaline etchants which are suitable for use in the present invention as either the first or the second alkaline etching bath or as both alkaline etching baths are as follows:

Water (deionized) liters 57.6 Potassium hydroxide kilograms 24.8

The aluminum sheet is immersed in this etchant for one to three minutes, preferably two minutes, at a temperature of 60 C. to 80 C., preferably 70 C., and the components of the etchant can be varied within a range from +20 percent to -20 percent.

Water (deionized) liters 66.68 Potassium hydroxide kilograms 5.80 Glycerine liters 33.34

The aluminum sheet is immersed in this etchant for one to three minutes, preferably two minutes, at a temperature of 40 C. to 80 C., preferably 60 C., and the components of the etchant can be varied within a range from +20 percent to --20 percent.

Water liters 50 Tri-sodium phosphate kilogram .25 Sodium hydroxide do .75 Sodium carbonate do .25

The aluminum sheet is immersed in this etchant for one to three minutes, preferably two minutes, at a temperature of 65 C. to 85 C., preferably C., and the components of the etchant can be varied within a range from +20 percent to -20 percent.

Water liters 50 Tri-sodium phosphate kilogram .25 Potassium hydroxide do .75 Potassium carbonate do .25

The aluminum sheet is immersed in this etchant for one to three minutes, preferably two minutes, at a temperature of 65 C. to 85 C., preferably 75 C., and the components of the etchant can be varied within a range from +20 percent to ---20 percent.

Water liters 66.68 Potassium hydroxide kilograms 5.80 Ethylene glycol liters 33.34

The aluminum sheet is immersed in this etchant for one to three minutes, preferably two minutes, at a temperature of 40 C. to C., preferably 60 C., and the components of the etchant can be varied within a range from +20 percent to 20 percent.

Water liters 66.68 Sodium hydroxide kilograms 5.80 Ethylene glycol liters 33.34

The aluminum sheet is immersed in this etchant for one to three minutes, preferably two minutes, at a temperature of 40 C. to 80 C., preferably 60 C., and the components of the etchant can be varied within a range from +20 percent to -20 percent.

Additional acid etchants which are suitable for use in the present invention are as follows:

Liters Water (deionized) 48.4 Phosphoric acid (85%) 48.4 Fluoboric acid (48%) 1.8

The aluminum sheet is immersed in this etchant for one to three minutes, preferably two minutes, at a temperature of 40 C. to 80 C., preferably 60 C., and the components of the etchant can be varied within a range from +20 percent to 20 percent.

Liters Water (deionized) 48.4 Phosphoric acid (85%) 48.4 Fluosilicic acid (30%) 4.8

The aluminum sheet is immersed in this etchant for one to three minutes, preferably two minutes, at a temperature of 40 C. to 80 C., preferably 60 C., and the components of the etchant can be varied within a range from +20 to- 20 percent.

Liters Water (deionized) 48.4 Phosphoric acid (85%) 48.4 Hydrobromic acid (47%) 1.6

The aluminum sheet is immersed-in this etchant for one to three minutes, preferably two minutes, at a temperature of 60 C. to 80 C., preferably 70 C., and the components of the etchant can be varied within a range from +20 percent to -20 percent.

Liters Water (deionized) 48.4 Sulfuric acid (98%) 48.4 Hydrofluoric acid (52%) 3.8

The aluminum sheet is immersed in this etchant for one to three minutes, preferably two minutes, at a temperature of 40 C. to 80 C., preferably 60 C., and the components of the etchant can be varied within a range from +20 percent to -20 percent.

Liters Water (deionized) 48.4 Sulfuric acid (98%) 48.4 Fluoboric acid (48%) 1.8

The aluminum sheet is immersed in this etchant for one to three minutes, preferably two minutes, at a temperature of 40 C. to 80 C., preferably 60 C., and the components of the etchant can be varied within a range from +20 percent to 20 percent.

Liters Water (deionized) 48.4 Sulfuric acid (98%) 48.4 Fluosilicic acid (30%) 4.8

The aluminum sheet is immersed in this etchant for one to three minutes, preferably two minutes, at a temperature of 40 C. to 80 C., preferably 60 C., and the components of the etchant can be varied within a range from +20 percent to -20 percent.

Liters Water (deionized) 48.4 Sulfuric acid (98%) 48.4 Hydrochloric acid (36%) 3.2

The aluminum sheet is immersed in this etchant for one to three minutes, preferably two minutes, at a temperature of 60 C. to 80 C., preferably 70 C., and the components of the etchant can be varied within a range from +20 percent to -20 percent.

Liters Water (deionized) 48.4 Nitric acid (70%) 48.4 Fluoboric acid (48%) 1.8

The aluminum sheet is immersed in this etchant for one to three minutes, preferably two minutes, at a tem- 6 perature of 40 C. to C., preferably 60 C., and the components of the etchant can be varied within a range from +20 percent to -20 percent.

Liters Water (deionized) 48.4 Nitric acid (70%) 48.4 Fluosilicic acid (30%) 4.8

The aluminum sheet is immersed in this etchant for one to three minutes, preferably two minutes, at a temperature of 40 C. to 80 C., preferably 60 C., and the components nents of the etchant can be varied within a range from +20 percent to 20 percent.

Liters Water (deionized) 48.4 Nitric acid (70%) 48.4 Hydrofluoric acid (52%) 3.8

The aluminum sheet is immersed in this etchant for one to three minutes, preferably two minutes, at a temperature of 40 C. to 80 C., preferably 60 C., and the components of the etchant can be varied within a range from +20 percent to 20 percent.

Liters Water (deionized) 48.4 Nitric acid (70%) 48.4 Hydrochloric acid (36%) 3.2

The aluminum sheet is immersed in this etchant for one to three minutes, preferably two minutes, at a temperature of 60 C. to 80 C., preferably 70 C., and the components of the etchant can be varied within a range from +20 percent to 20 percent.

All the foregoing alkaline and acid etchants can be advantageously used both on 28 (1100) aluminum sheets and 3S (3003) aluminum sheets. In the case of the alkaline etchants any two thereof can be used as the first and sec-0nd alkaline etchants in any order and each of the alkaline etchants can be used for both etching baths. Any of the alkaline etchants can be used with any of the acid etchants.

What is claimed is:

1. A process for chemically graining an aluminum lithographic plate on both sides to produce a superior grain structure of uniform and streakless characteristics which comprises immersing the surfaces of such plate in an alkaline etchant to produce a pited surface, then in an acid etchant to deepen the pits and form hills and valleys with sharp peaks, and then again in an alkaline etchant to remove the fine fragile peaks and to dissolve water-insoluble film left by the acid etchant.

2. A process for chemically graining an aluminum lithographic plate on both sides to produce a superior grain structure of uniform and streakless characteristics which comprises immersing the surfaces of such plate in an aqueous alkaline etchant based on an alkali selected from the group consisting of sodium hydroxide and potassium hydroxide to produce a pitted surface, then in an aqueous solution of a mineral acid to cause acid etching and to deepen the pits and form hills and valleys with sharp peaks and then again in an aqueous alkaline etchant based on an alkali selected from the group consisting of sodium hydroxide and potassium hydroxide to remove the fine fragile peaks and to dissolve water-insoluble film left by the acid etchant.

3. A process for chemically graining an aluminum lithographic plate on both sides to produce a superior grain structure of uniform and streakless characteristics which comrpises immersing such plate in an alkaline etchant made up of Water, sodium hydroxide and glycerine at a temperature of 50 C. to 70 C. for one to three minutes to produce a pitted surface, then in an acid etchant made up of Water, phosphoric acid and hydrofluoric acid at a temperature of 60 C. to 80 C. for one to three minutes to deepen the pits and form hills and valleys with sharp peaks, .and then again in the same alkaline etchant under the same conditions to remove the fine fragile peaks and dissolve water-insoluble film left by the acid etchant.

4. A process for chemically graining an aluminum lithographic plate on both sides to produce a superior grain structure of uniform and streakless characteristics Which comprises immersing such plate in an alkaline etchant made up of Water, sodium hydroxide and glycerine at a temperature of 50 C. to 70 C. for one to three minutes to produce a pitted surface, then in an acid etchant made up of water and hydrochloric acid at a temperature of 55 C. to 75 C. for ten to twenty seconds to deepen the pits and form hills and valleys with sharp peaks, and then in an alkaline etchant made up of water and sodium hydroxide to remove the fine fragile peaks and dissolve water-insoluble film left by said etchant.

5. A process for chemically graining an aluminum lithographic plate on both sides to produce a superior grain structure of uniform and streakless characteristics which comprises immersing such plate in an alkaline etchant made up of Water, sodium hydroxide and glycerine at a temperature of 50 C. to 70 C. for one to three minutes to produce a pitted surface, then in an acid etchant made up of water, phosphoric acid and hydrochloric acid at a temperature of 60 C. to 80 C. for one to three minutes to deepen the pits and form hills and valleys with sharp peaks, and then again in the same alkaline etchant under the same conditions to remove the fine fragile peaks and dissolve Water-insoluble film left by the acid etchant.

6. A process for chemically graining an aluminum lithographic plate on both sides to produce a superior grain structure of uniform and streakless characteristics Which comprises immersing the surfaces of such plate in an alkaline etchant to produce a pitted surface, then in an acid etchant to deepen the pits and form hills and valleys with sharp peaks, and then again in an alkaline etchant to remove the fine fragile peaks and to dissolve water-insoluble film left by the acid etchant, and subjecting the thus grained plate to a non-etching acid bath to remove the smut produced by the last alkaline etchant.

7. A process for chemically graining an aluminum lithographic plate on both sides to produce a superior grain structure of uniform and streakless characteristics Which comprises immersing the surfaces of such plate in an alkaline etchant to produce a pitted surface, then in an acid etchant to deepen the pits and form hills and valleys with sharp peaks, and then again in an alkaline etchant to remove the fine fragile peaks and to dissolve water-insoluble film left by the acid etchant, and subjecting the thus grained plate to a non-etching acid bath to remove the smut produced by the last alkaline etchant, said de-smutting bath being made up of deionized water and nitric acid.

8. A process for chemically graining an aluminum lithographic plate on both sides to produce a superior grain structure of uniform and streakless characteristics which comprises immersing said plate for one to three minutes at 50 C. to 70 C. in an aklaline etchant prepared by mixing the following components in the order listed and in the proportions stated:

Water (deionized) liters 66.68 Sodium hydroxide kilograms 5.80 Glycerine liters 33.34

said components of the etchant can be varied within a range from +20% to 20%, removing the plate from the etchant, rinsing it for one to three minutes at 60 C. to 80 C. in an acid etchant prepared by mixing the following components in the order listed and in the proportions stated:

Liters Water (deionized) 48.40 Phosphoric acid (85%) 48.40 HydrofluOric acid (53%) 3.20

said components of the etchant can be varied within a range from +20% to 20%, removing the plate from the acid etchant, rinsing it With deionized water at room temperature, again immersing it in the same alkaline etchant under the same conditions, rinsing the thus treated plate with deionized water at room temperature and immersing it in a desmutting bath at room temperature for twenty to forty seconds, said desmutting bath being composed of 50 liters of deionized Water and 50 liters of 70 percent nitric acid, and finally rinsing and drying the plate.

9. A process for chemically gaining an aluminum lithographic plate on both sides to produce a superior grain structure of uniform and streakless characteristics which comprises immersing the plate for one to three minutes at 50 C. to 70 C. in an alkaline etchant prepared by mixing the following components in the order listed and in the proportions stated:

Water (deionized) liters 66.68 Sodium hydroxide kilograms 580 Glycerine liters 33.34

said components of the etchant can be varied within a range from +20% to 20%, removing the plate from the alkaline etchant, rinsing it with deionized water at room temperature, immersing it for ten to twenty seconds at 55 C. to 70 C. in an acid etchant composed of:

Liters Water (deionized) 67 Hydrochloric acid (36%) 33 said components of the etchant can be varied within a range from +15% to 15%, removing the plate from the acid etchant, rinsing it with deionized water at room temperature, immersing it for one to three minutes at 67 C. to 87 C. in an alkaline etchant composed of:

Water (deionized) liters 57.6 Sodium hydroxide kilograms 24.8

said components of the etchant can be varied within a range from +20% to 20%, removing the plate from the alkaline etchant, rinsing it with deionized water at room temperature, and immersing it in a desmutting bath at room temperature for twenty to forty seconds, the said desmutting bath being composed of 50 liters of deionized water and 50 liters of 70 percent nitric acid, and then rinsing and drying said plate.

10. A process for chemically graining an aluminum lithographic plate on both sides to produce a superior grain structure of uniform and streakless characteristics which comprises immersing said plate for one to three minutes at 50 C. to 70 C. in an alkaline etchant prepared by mixing the following components in the order listed and in the proportions stated:

Water (deionized) liters 66.68 Sodium hydroxide kilograms 5.80 Glycerine liters 33.34

said components of the etchant can be varied within a range from +20% to 20%, removing the plate from the etchant, rinsing it with deionized water at room temperature, immersing it for one to three minutes at 60 C. to C. in an acid etchant prepared by mixing the following components in the order listed and in the proportions stated:

Liters Water (deionized) 48.40 Phosphoric acid 48.40 Hydrochloric acid (36%) 3.20

said components of the etchant can be varied within a range from +20% to +20%, removing the plate from the acid etchant, rinsing it with deionized water at room temperature, again immersing it in the same alkaline etchant under the same conditions, rinsing the thus treated plate with deionized water at room temperature and immersing it in a desmutting bath at room temperature for twenty to forty seconds, said desmutting bath being composed of 50 liters of deionized water and '50 liters of 70 percent nitric acid, and finally rinsing and drying the plate.

11. A process for chemically graining an aluminum lithographic plate on both sides to produce a superior gain structure of uniform and streakless characteristics which comprises immersing the surfaces of such plate in an alkaline etchant to produce a pitted surface, then in an acid etchant to deepen the pith and form hills and valleys with sharp peaks, and then again in an alkaline etchant to remove the fine fragile peaks and to dissolve water-insoluble film left by the acid etchant, said alkaline etchants being selected from the group consisting of:

Water (deionized) liters 66.68 Sodium hydroxide kilograms 5.80 Glycerine liter 33.34

Water (deionized) liters 57.6 Sodium hydroxide kilograms 24.8

Water (deionized) liters 57.6 Potassium hydroxide kilograms 24.8

Water (deionized) liters 66.68 Potassium hydroxide kilograms 5.80 Glycerine liters 33.34

Water liters 50 Tri-sodium phosphate kilograms .25 Sodium hydroxide do .75 Sodium carbonate do .25

Water liters 50 Tri-sodium phosphate kilograms .25 Potassium hydroxide do .75 Potassium carbonate do .25

Water liters 66.68 Potassium hydroxide kilograms 5.80 Ethylene glycol liters 33.34

Water liters 66.68 Sodium hydroxide kilograms 5.80 Ethylene glycol liters 33.34

12. A process for chemically graining an aluminum lithographic plate on both sides to produce a superior grain structure of uniform and streakless characteristics which comprises immersing the surfaces of such plate in an alkaline etchant to produce a pitted surface, then in an acid etchant to deepen the pits and form hills and valleys with sharp peaks, and then again in an alkaline etchant to remove the fine fragile peaks and to dissolve water-insoluble film left by the acid etchant, said acid etchant being selected from the group consisting of:

Liters Water (deionized) 48.40 Phosphoric acid (85%) 48.40 Hydrofluoric acid (53%) 3.20

Water (deionized) 67 Hydrochloric acid (36%) 33 Water (deionized) 48.40 Phosphoric acid (85%) 48.40 Hydrochloric acid (36%) 3.20

Water (deionized) 48.4 Phosphoric acid (85%) 48.4 Fluoboric acid (48%) 1.8

Water (deionized) 48.4 Phosphoric acid (85%) 48.4 Fluosilicic acid (30%) 4.8

Water (deionized) 48.4 Phosphoric acid (85%) 48.4 Hydrobromic acid (47%) 1.6

Water (deionized) 48.4 Sulfuric acid (98%) 48.4 Hydroflnoric acid (52%) 3.8

Liters Water (deionized) 48.4 Sulfuric acid (98%) 48.4 Fluoboric acid (48%) 1.8

Water (deionized) 48.4 Sulfuric acid (98%) 48.4 Fluosilicic acid (30%) 4.8

Water (deionized) 48.4 Sulfuric acid (98%) 48.4 Hydrochloric acid (36%) 3.2

Water (deionized) 48.4 Nitric acid (70%) 48.4 Fluoboric acid (48%) 1.8

Water (deionized) 48.4 Nitric acid (70%) 48.4 Fluosilicic acid (30%) 4.8

Water (deionized) 48.4 Nitric acid (70%) 48.4 Hydrofiuoric acid (52%) 3.8

Water (deionized) 48.4 Nitric acid (70%) 48.4 Hydrochloric acid (36%) 3.2

13. A process for chemically graining an aluminum lithographic plate on both sides to produce a superior grain structure of uniform and streakless characteristics which comprises immersing the surfaces of such plate in an alkaline etchant to produce a pitted surface, then in an acid etchant to deepen the pits and form hills and valleys with sharp peaks, and then again in an alkaline etchant to remove the fine fragile peaks and to dissolve water-insoluble film left by and acid etchant, said alkaline etchants being selected from the group consisting of:

Water (deionized) liters 66.68 Sodium hydroxide kilograms 5.80 Glycerine liters 33.34

Water (deionized) liters 57.6 Sodium hydroxide kilograms 24.8

Water (deionized) liters 57.6 Potassium hydroxide kilograms 24.8

Water (deionized) liters 66.68 Potassium hydroxide kilograms 5.80 Glycerine liters 33.34

Water liters 50 Tri-sodium phosphate kilograms .25 Sodium hydroxide do .75 Sodium carbonate do .25

Water liters 50 Tri-sodium phosphate kilograms .25 Potassium hydroxide do .75 Potassium carbonate do .25

Water liters 66.68 Potassium hydroxide kilograms 5.80 Ethylene glycol liters 33.34

Water liters 66.68 Sodium hydroxide kilograms 5.80 Ethylene glycol liters 33.34

and said acid etchant being selected from the group consisting of:

Liters Water (deionized) 48.40 Phosphoric acid 48.40 Hydrofluoric acid (53%) 3.20

Water (deionized) 67 Hydrochloric acid (36%) 33 Water (deionized) 48.40 Phosphoric acid (85 48.40 Hydrochloric acid (36%) 3.20

Liters Water (deionized) 48.4 Phosphoric acid (85%) 48.4 Fluoboric acid (48%) 1.8

Water (deionized) 48.4 Phosphoric acid (85%) 48.4 Fluosilicic acid (30%) t 4.8

Water (deionized) 48.4 Phosphoric acid (85%) 48.4 Hydrobromic acid (47%) 1.6 Water (deionized) 48.4 Sulfuric acid (98%) 48.4 Hydrofluoric acid (52%) 3.8

Water (deionized) 48.4 Sulfuric acid (98%) 48.4 Fluoboric acid (48%) 1.8 Water (deionized) 48.4 Sulfuric acid (98%) 48.4 Fluosilicic acid (30%) 4.8

Water (deionized) 48.4 Sulfuric acid (98%) 48.4 Hydrochloric acid (36%) 3.2

Water (deionized) 48.4 Nitric acid (70%) 48.4 Fluoboric acid (48%) 1.8

. Liters Water (deionized) 48.4

Nitric acid (70%) 48.4

Fluosilicic acid 4.8

Water (deionized) 48.4

Nitric acid 48.4

Hydrofluoric acid (52%) 3.8

Water (deionized) 48.4

Nitric acid (70%) 48.4

Hydrochloric acid (36%) 3.2

References Cited by the Examiner UNITED STATES PATENTS 2,180,798 11/1939 Collins 156-23 2,396,685 3/1946 Coggins 15623 2,507,314 5/1950 Mason 156-23 XR 2,650,157 8/1953 Cochran 15621 2,699,382 1/1955 Altenpohl 15622 2,942,955 6/1960 Hannah 156 -22 3,010,854 11/1961 Satterfield 156-22, 3,085,917 4/1963 Netzler et a1. 252-79.3 XR

ALEXANDER WYMAN, Primary Examiner.

JACOB STEINBERG, Examiner, 

1. A PROCESS FOR CHEMICALLY GRAINING AN ALUMINUM LITHOGRAPHIC PLATE ON BOTH SIDES TO PRODUCE A SUPERIOR GRAIN STRUCTURE OF UNIFORM AND STREAKLESS CHARACTERISTICS WHICH COMPRISES IMMERSING THE SURFACE OF SUCH PLATE IN AN ALKALINE ETCHANT TO PRODUCE A PITED SURFACE, THEN IN AN ACID ETCHANT TO DEEPEN THE PITS AND FORM HILLS AND VALLEYS WITH SHARP PEAKS, AND THEN AGAIN IN AN ALKALINE ETCHANT TO REMOVE THE FINE FRAGILE PEAKS AND TO DISSOLVE WATER-INSOLUBLE FILM LEFT BY THE ACID ETCHANT. 